Preparation and characterization of mixed hydroxy-Fe-Al pillared montmorillonite with large basal spacing

Mixed hydroxy-Al-Fe pillared montmorillonites with large basal spacing were successfully prepared through cation-exchanging of Na +- montmorillonite with mixed hydroxy-Al and hydroxy-Fe pillaring solutions made from hydrolysis of corresponding metal salts, followed by calcination to convert hydroxy-Al and hydroxy-Fe into intercalated polycations. According to XRD analysis, the basal spacing d(001) of pillared products dramatically enlarged from 12.7 *! in the Na-montmorillonite to 81 *! in the hydroxy-Fe -montmorillonite and 77.5 *! in mixed hydroxy-Al-Fe-montmorillonite. The N_2 BET surface areas of the pillared montmorillonites also greatly increased to more than 200 m 2/g as compared to about 27 m 2/g for the Na-montmorillonite. IR analysis of hydroxy-Fe, and mixed hydroxy-Al-Fe pillared montmorillonites revealed a new absorption vibration at 1384 cm -1 wavelength. XRF elemental analysis data also showed a high content of Fe_2O_3 in the hydroxy-Fe pillared montmorillonite.

Preparation and Characterization of Hydroxyiron-Montmorillonite Complexes

Hydroxy Fe ions react slowly with montmorillonite by intercalation into their interlayer space and adsorption on their surface to form various hydroxyiron montmorillonite complexes. Hydroxyiron montmorillonite complexes are assumed to have the ability to adsorb anions such as H 2PO - 4, HPO 2- 4, CrO 2- 4, CrO - 2, H 2AsO - 4, HAsO 2- 4 , AsO 3- 4 and F -, which may come from weathered rocks or waste industrial water, and result in concentration of P, Cr, As and F in soil. In this paper, hydroxy Fe ions including Fe(OH) 2+ , Fe(OH) + 2 and Fe 2(OH) 2+ 2 are prepared through hydrolysis of iron in acid solutions with different pH values. Corresponding hydroxyiron montmorillonite complexes are obtained by intercalation and adsorption of these hydroxy Fe ions into the interlayer space and on the surface of montmorillonite. The obtained hydroxyiron montmorillonite complexes are characterized with XRD and DTA, showing that they have similar basal space and thermal stability with Fe montmorillonite.

Fe(II)改性蒙脱石对土壤汞的吸附固定机理探究

为明确Fe-MMT对土壤汞离子(Hg^(2+))的吸附、解吸特性及潜在作用机理,采用FeSO_(4)·7H_(2)O改性钠基蒙脱土(Na-MMT),合成了Fe(II)基蒙脱石(Fe-MMT),并探究了不同pH值、吸附剂用量、Hg^(2+)初始浓度和反应时间等条件下,Fe-MMT对土壤Hg^(2+)的吸附解吸特性、吸附动力学和等温吸附模型。结果发现:在pH=5、吸附剂用量为0.5 g、Hg^(2+)初始浓度为170 mg/L、反应时间为0.5 h的条件下,Fe-MMT对土壤Hg^(2+)的去除率高达76.8%;Fe-MMT对Hg^(2+)+的吸附过程符合Langmuir等温吸附模型,伪二阶动力学模型可较好地拟合吸附动力学行为,表明该吸附过程主要为单分子层吸附,且主要发生在吸附剂表面的均相反应位点上;结合微观结构表征,发现Fe-MMT对土壤Hg^(2+)的吸附主要通过-S^(2-)、-SH和-OH与Hg^(2+)进行络合,以及Fe^(2+)与Hg^(2+)的原位共沉淀络合引起的;Fe-MMT在水-土混合体系中的解吸率为9.7%,表明Fe-MMT对土壤Hg^(2+)具有较强的固定作用。可见,Fe-MMT具有修复Hg污染土壤的潜力。

Al-Fe柱撑膨润土的制备及其对活性艳红X-3B的吸附

利用 Fe3+,Al3+与碱液反应制备出 OH- Fe离子、Keggin离子 ,并由此制备出不同 Fe/ ( Al+Fe)比值的 Al- Fe柱撑膨润土 ,并对其吸附有机染料——活性艳红 X- 3B的效果作了研究 (与其他几种改性膨润土进行了比较 ) .结果表明 :用 Al- Fe柱撑膨润土的层间距被明显撑大 ,有机污染物的去除率高 .

羟基Fe、Al柱撑蒙脱石对庆大霉素的吸附行为

以蒙脱石(Mont)为原料,在不同OH/Fe物质的量比(x)和Fe/Al物质的量比(y)柱撑条件下制备出系列羟基铁(x OH/Fe-Mont)、羟基铝(OH/Al-Mont)和羟基铁铝(y Fe/Al-Mont)柱撑蒙脱石,采用XRD和FT-IR对柱撑蒙脱石进行表征,并研究了柱撑改性对蒙脱石对庆大霉素(Gen)吸附行为的影响.结果表明:柱撑蒙脱石对Gen吸附量显著提高,且Mont(42.83mg/g)<<OH/Al-Mont(63.50mg/g)<1.5OH/FeMont(70.50mg/g)<<0.025Fe/Al-Mont(87.20mg/g),吸附Gen最佳p H值为9.等温吸附适于采用Freundlich方程拟合,吸附动力学符合伪二级动力学方程,吸附3h可超过平衡吸附量的80%.XRD分析表明,羟基铁和羟基铝主导柱撑(y≤0.5)蒙脱石层间距扩增是吸附量增加的主要原因,而y Fe/Al-Mont中y≥1.0时,层间距并不是吸附量变化的的主导机制;FT-IR分析表明阳离子交换是Gen和铝离子进入蒙脱石的主导机制.

Ni-Fe/蒙脱土催化剂催化乙醇水蒸气重整制氢的研究

采用浸渍法制备了一系列Ni-Fe/蒙脱土(MMT)催化剂,并应用于乙醇水蒸气重整制氢反应(ESR)。采用X射线衍射(XRD)、N_2吸附脱附分析和H_2-程序升温还原(H_2-TPR)表征手段对催化剂的物理化学性质、还原性能、碳沉积等进行了研究。结果表明,Ni-Fe/MMT催化剂中,Ni、Fe高度分散在载体MMT层间及表面,而且Fe的加入降低了Ni颗粒的粒径,增强了Ni^(2+)与载体的相互作用力。以10Ni5Fe/MMT为催化剂,在反应温度为500℃、水醇比为3∶1、空速为12 h^(-1),反应进行30 h后,乙醇转化率为100%,氢气选择性仍保持72%,副产物CO和CH_4含量明显降低。这是因为催化助剂Fe的引入,一方面,提高了Ni的分散度,使得ESR低温活性较好;另一方面,减小了Ni颗粒粒径,小颗粒的Ni有利于抑制甲烷的生成,并且Fe的加入加强了甲烷重整和水煤气变换反应,提高产物中氢气的选择性。

Fe-SDS-柱撑蒙脱石制备与吸附镉的实验研究

以天然的钙基蒙脱石为基质,在超声波处理的条件下制备了新型的十二烷基硫酸钠(SDS)-铁复合柱撑蒙脱石,并采用X射线粉末衍射(XRD)、红外光谱(FT-IR)和热重(TGA)对其进行表征。研究了镉在复合柱撑蒙脱石上的吸附特性,从动力学角度探讨了吸附机理。结果表明,吸附过程符合准二级动力学方程,化学吸附控制了吸附过程的速度,且平衡吸附量qe与平衡浓度eρ之间的关系符合Langmuir等温方程。

Fe/Cr柱撑蒙脱石的水热法制备与表征

以钙基蒙脱石为原料,经超声波预处理后,利用水热法合成了Fe/Cr柱撑蒙脱石。水热法与传统方法相比,可以省去钠化改型和老化等步骤,大大缩短制备周期。在水热法制备柱化剂的过程中,首次提出二次水解法。实验结果表明,经过预处理后,蒙脱石的分散度大大提高,平均粒度达0.964μm;二次水解法可以制备出更好的柱化剂。XRD和XRF分析结果表明,水热法可以制备出结晶较好、热稳定性较高和具有良好孔结构的柱撑蒙脱石,经过二次水解法制备的Fe/Cr柱撑蒙脱石的d(001)达1.962 nm。

蒙脱石中Fe^(3+)离子状态研究

分析了蒙脱石样品的穆斯堡尔谱,发现蒙脱石层中铁原子的成分主要为Fe3+ 阳离子.从穆斯堡尔谱拟合出的Fe3+ 二套四极双峰表明,铁在蒙脱石中占据着两种不同的八面体位置.

阪崎克洛诺菌还原蒙脱石中Fe^(3+)实验研究

为研究阪崎克洛诺菌(Cronobacter Sakazakii)还原普通钙基蒙脱石中Fe3+的过程与机理,测定了体系中总蛋白与Fe2+含量变化,应用同步辐射XRD(SRXRD)与X射线吸收近边结构(XANES)研究反应产物。总蛋白与Fe2+数据表明在厌氧条件下Cronobacter sakazakii以乙酸作为电子供体,利用钙基蒙脱石中Fe3+作为电子受体进行生长代谢,还原蒙脱石中Fe3+形成Fe2+。反应中蒙脱石晶体结构部分破坏,原始的d001峰消失,出现一系列与新生矿物有关的衍射峰。XANES结果显示蒙脱石中Fe主吸收峰向低能量方向移动0.5 e V,边前峰峰位中心向低能量方向移动且峰面积减小,Fe氧化态降低,蒙脱石晶体结构发生变化。研究探讨了自然界中广泛分布的钙基蒙脱石可能受到的微生物还原作用。

黏土矿物界面吸附Fe(Ⅱ)耦合对邻硝基苯酚还原转化的增强机理研究

系统考查了Fe(Ⅱ)分别与高岭石、蒙脱石结合的界面结合系统对邻硝基苯酚(简称2-NP)的还原转化作用。研究表明,矿物表面结合态Fe(Ⅱ)能够有效提高2-NP的还原转化速率,2-NP的还原反应符合伪一级反应动力学方程,而且速率常数(k)随溶液pH值、亚铁离子初始浓度以及反应温度的升高而显著增大。当温度25℃,pH值6.7,Fe(Ⅱ)和2-NP初始浓度分别为3.0 mmol/L、0.022 mmol/L,以及黏土的投加量为4.0 g/L时,Fe(Ⅱ)/高岭石系统对2-NP的还原转化率在4.0 h内可达到100%。同样,pH值从6.0升高至7.3时,Fe(Ⅱ)/蒙脱石系统对2-NP的还原转化也显著增强;但在较低pH值和较低初始Fe(Ⅱ)浓度时,蒙脱石对Fe(Ⅱ)的还原催化性能不如高岭石,可归因于蒙脱石具有较高的离子交换性能。因此,Fe(Ⅱ)在上述两种矿物上吸附形态的差异是导致该系统对2-NP还原转化出现不同效应的根本原因。

Fe^(3+)-Co^(2+)掺杂的蒙脱土吸附邻苯二甲酸二丁酯的性能研究

目的:探索双金属离子Fe^(3+)-Co^(2+)共同掺杂的改性蒙脱土(Fe^(3+)-Co^(2+)-MMT),吸附邻苯二甲酸二丁酯(DBP)的性能。方法:Fe^(3+)-Co^(2+)与Na+在常压下进行离子交换而制得Fe^(3+)-Co^(2+)-MMT,以DBP的去除率为评价指标,应用单因素实验优化Fe^(3+)-Co^(2+)-MMT的吸附条件。结果:当铁钴离子掺杂总量为2g/L、铁钴离子掺杂比例为1.2∶0.8时所制得的改性蒙脱土,在DBP浓度为0.08mg/mL、35℃、吸附140min时吸附性能最佳,DBP的去除率可达到89.84%。结论:Fe^(3+)-Co^(2+)-MMT显示了较强的吸附DBP的能力,远高于未改性的Na-MMT(64.40%),亦高于Fe^(3+)或Co^(2+)单独掺杂的改性蒙脱土。

Fe改性Zr基蒙脱土对新疆和丰煤热解行为的影响

采用机械球磨法制备不同Fe盐改性Zr基蒙脱土催化剂,通过X射线衍射仪(XRD)、物理吸附仪(BET)、化学吸附仪(NH_(3)-TPD、H2-TPR)和X射线光电子能谱仪(XPS)分析其组成和结构。结果表明,与24ZrAM相比,以FeCl_(3)·6H2O和FeCl2·4H2O为铁源时,3Cl−-24ZrAM和2Cl−-24ZrAM中生成了Fe–O–Zr结构。Fe的硫酸盐存在时,催化剂的比表面积显著减小。引入Fe后,催化剂的总酸量均降低,3Cl−-24ZrAM的酸量与强酸强度最高。H2-TPR显示,3Cl−-24ZrAM、2Cl−-24ZrAM和3NO_(3)^(-)-24ZrAM中Fe2O3还原为Fe3O4的温度均低于500℃。在固定床反应器中考察了催化剂对新疆和丰煤热解行为及含不同桥键模型化合物的断键机制的影响。与24ZrAM相比,不同Fe源改性蒙脱土均能降低焦油中沥青的质量分数,其中,3Cl−-24ZrAM的裂解活性最高,轻质焦油分率增加至63%,比24ZrAM提高了18.9%,轻油和酚油质量分数分别为24ZrAM的1.3倍和1.4倍,长链烃含量进一步降低,降幅为0.7%。引入Fe后,苄基苯基醚(BPE)、联苄和联苯的转化率分别比24ZrAM提高了5%、1.6%和43.9%。

Adsorption of Direct Green B on mixed hydroxy-Fe-Al pillared montmori llonite with large basal spacing

Through cation exchanging of montmorillonite, mixed hydroxy Fe Al pillared montmorillonites with large basal spacing were synthesized. The application of these mixed hydroxy Fe Al pillared montmorillonites as adsorbents in the areas of environmental protection and pollution control was investigated. Adsorption of Direct Green B, an organic dye, on OH—Fe—, OH—Al—, OH—Fe—Al— pillared montmorillonites was studied. Results showed that these pillared montmorillonites had much better adsorption properties than traditional Na organo montmorillonite. It was also found that pH of the solutions had great effect on the performance of these hydroxy metal pillared montmorillonites in treating the wastewater containing Direct Green B.

Fe/Zr柱撑蒙脱石制备方法及其层间结构特征对比研究

用两种不同的方法制备聚合羟基Fe/Zr柱撑蒙脱石,一是(a组)先将钙基蒙脱石用十六烷基三甲基溴化铵(CTAB)有机改性得到有机柱撑蒙脱石,然后用不同摩尔比的聚合羟基Fe/Zr阳离子进行柱撑反应,制得Fe/ZrCTAB柱撑蒙脱石;二是(b组)先将钙基蒙脱石钠化再制备Fe/Zr柱撑蒙脱石的方法。将制得的柱撑蒙脱石在500℃下焙烧4h,并利用X射线衍射分析﹑热重及傅里叶红外光谱分析、N2吸附测比表面积,研究合成产物的层间结构特性。结果表明:钠化的蒙脱石和有机改性的蒙脱石制得的聚合羟基柱撑蒙脱石具有明显不同的特性,用CTAB改性的蒙脱石制备的柱撑蒙脱石的聚合羟基金属阳离子柱撑均匀,层间结构均一,且经过焙烧的柱撑蒙脱石都具备较好的稳定性;由钠化的蒙脱石制得的聚合羟基柱撑蒙脱石的层间距较大,具有丰富的层状纳米结构和高比表面积。

还原态蒙脱石结构Fe(Ⅱ)催化水铁矿转化特性及影响因素

还原条件下土壤中Fe(Ⅱ)催化水铁矿转化在调控营养元素和污染物的生物地球化学过程中具有重要作用。然而,作为土壤中Fe(Ⅱ)存在的主要形态之一,蒙脱石结构中Fe(Ⅱ)催化水铁矿转化的特性及其影响因素目前尚不清楚。以化学还原的蒙脱石为研究对象,探究还原态蒙脱石(rSWy-2)结构中Fe(Ⅱ)催化水铁矿转化的特性及其影响因素。结果表明,贫铁的蒙脱石结构中Fe(Ⅱ)可催化水铁矿向纤铁矿转化,反应96 h后水铁矿转化量达到83.3%。X射线衍射(XRD)、高分辨透射(HRTEM)、球差电镜(STEM)和表面吸附态Fe(Ⅱ)含量分析表明,rSWy-2结构Fe(Ⅱ)催化水铁矿转化主要经历矿物间固相吸附、电子传递和水铁矿转化三个阶段,形成的纤铁矿呈板状纳米片,尺寸大小为100~200 nm。溶液中Na^(+)和Cl^(-)离子对rSWy-2催化水铁矿转化影响较弱,而Ca^(2+)、SO_(4)^(2-)、有机质和As(Ⅲ)均对水铁矿转化具有明显的抑制作用。

Adsorption of As on hydroxy-Fe-montmorillonite complexes

Arsenate has high affinity for soluble hydroxy-Fe species and Fe-oxyhydroxide pre-cipitates. In addition, the hydrolysis of Fe(III) and the growth of the initially precipitated Fe(III) phases are strongly influenced by the presence of montmorillonite. In this paper, the adsorption of As onto various hydroxy-Fe-montmorillonite (H-F-M) complexes was studied. Three systems of samples were prepared by mixing montmorillonite, hydroxy-Fe and arsenate in different se-quences: (1) Prior mixing of montmorillonite and hydroxy-Fe before the addition of arsenate; (2) prior mixing of hydroxy-Fe and arsenate before the addition of montmorillonite; and (3) prior mixing of montmorillonite and arsenate before the addition of hydroxy-Fe. For each system, the effects of pH, ionic strength, temperature, initial Fe and As concentrations and adsorption dura-tion on the overall uptake of As by H-F-M complexes were studied. Results showed that the up-take of As increased with increasing pH, temperature, initial Fe concentration and adsorption duration, and decreased with increasing ionic strength and initial As concentration to different extents for the three systems. The variation of the As uptake of H-F-M complexes with pH in the range of study is opposite to that reported previously for Fe-O-H systems in the absence of montmorillonite and similar to that reported for montmorillonite in the absence of hydroxy-Fe. The marked influence of ionic strength on the As uptake of H-F-M complexes indicates that outer-sphere complexation plays an important role. This is quite different from the adsorption of As on the surface of either Fe-oxyhydroxides or montmorillonite alone in which inner-sphere complexation dominates. Under all experimental conditions, the H-F-M complexes studied dis-played a very strong affinity for As, among which system 2 had the highest As adsorption capac-ity and system 1 the lowest. The authors attribute this to the differences in mixing sequence which resulted in more hydroxy-Fe (the main adsorbent for As) in system 1 adsorbing onto montmorillonite before adsorbing As than in systems 2 or 3.

Thermal Decomposition Kinetics of High Impact Polystyrene/ Organo Fe-montmorillonite Nanocomposites

In this article, high impact polystyrene/organo Fe-montmorillonite （HIPS/Fe-OMT） nanocomposites were prepared by melting intercalation. The thermal stability of HIPS/Fe-OMT nanocomposites increased significantly compared to that of HIPS examined in thermal degradation conditions. Kinetic evaluations were performed by Kissinger, Flynn-Wall-Ozawa, Friedman methods and multivariate nonlinear regression. Apparent kinetic parameters for the overall degradation were determined. The resuRs showed that the activation energy of HIPS/Fe-OMT nanocomposites was higher than that of HIPS. A very good agreement between experimental and simulated curves was observed in dynamic conditions. Their decomposition reaction model was a single-step process of an nth-order reaction

低聚合羟基铁蒙脱石复合体吸附铬酸根的实验研究

在模拟的酸性土壤条件下,利用制备的低聚合羟基铁 蒙脱石复合体对铬酸根进行吸附实验。重点研究了吸附条件对复合体铬吸附能力的影响,对比了蒙脱石和含水氧化铁。结果表明,实验条件下复合体有较强的铬吸附能力,其铬吸附量低于铁沉积物而明显高于蒙脱石。铬初始质量浓度是影响复合体铬吸附量的最主要因素,离子强度次之。吸附时间(12h以上)、温度、pH值对复合体铬吸附量的影响很小;说明在酸性土壤条件下,复合体有强且稳定的铬吸附能力。

亚甲基蓝在钠、铝和铁蒙脱土上的吸附研究

研究了亚甲基蓝阳离子分别在钠、铝和铁蒙脱土上的吸附反应。结果表明，亚甲基蓝在三种蒙脱土上的吸附等温线均呈现 Ｌａｎｇｍ ｕｉｒ 型，但在低吸附量区域，钠蒙脱土上的吸附等温线发生了非单调变化。这反映不同交换性阳离子对蒙脱土的结构和性质有不同的影响，使粘土表面吸附分子层的分布和分子之间侧向作用力不同。由饱和吸附量计算了悬浮体中三种蒙脱土的比表面积。